A power supply device for a vehicle in which a plurality of power supplies are combined to supply electric power to a load is described in, for example, Japanese Patent Laying-Open No. 2008-54363 (PTD 1). PTD 1 describes controlling the state of charge of a power storage unit in the power supply device including a constant voltage source implemented by a battery and the power storage unit implemented by a storage element. Specifically, during a stop of the power supply device, voltage control is performed so as to leave the power storage unit at a voltage lower than that in the full state of charge, thereby elongating the life of the power storage unit.
Japanese Patent Laying-Open No. 2012-70514 (PTD 2) describes a configuration of a power converter capable of, by means of controlling of a plurality of switching elements, switching between an operation mode of carrying out DC/DC conversion with two DC power supplies connected in series (series connection mode) and an operation mode of carrying out DC/DC conversion with the two DC power supplies used in parallel (parallel connection mode).